Wells are generally drilled into the ground or ocean bed to recover natural deposits of oil and gas, as well as other desirable materials that are trapped in geological formations in the Earth's crust. Wells are typically drilled using a drill bit attached to the lower end of a “drill string.” Drilling fluid, or mud, is typically pumped down through the drill string to the drill bit. The drilling fluid lubricates and cools the bit, and may additionally carry drill cuttings from the borehole back to the surface.
In various oil and gas exploration operations, it may be beneficial to have information about the subsurface formations that are penetrated by a borehole. For example, certain formation evaluation schemes include measurement and analysis of the formation pressure and permeability. These measurements may be essential to predicting the production capacity and production lifetime of the subsurface formation.
Reservoir well production and testing may involve drilling into the subsurface formation and the monitoring of various subsurface formation parameters. When drilling and monitoring, downhole tools having electric, mechanic, and/or hydraulic powered devices may be used. In some implementations, pump systems may be used to draw and pump formation fluid from subsurface formations. A downhole string (e.g., a drill string, coiled tubing, slickline, wireline, etc.) may include one or more pump systems depending on the operations to be performed using the downhole string, or the string may have fluids pumped therein from a surface of the formation.
In a downhole flow analysis environment, the naturally occurring hydrocarbon fluids may include dry natural gas, wet gas, condensate, light oil, black oil, heavy oil, and heavy viscous tar. In addition, water and synthetic fluids, such as oils used within drilling muds, and fluids used in formation fracturing jobs, may also be present within the downhole environment.
As the economic value of a hydrocarbon reserve, the method of production, the efficiency of recovery, the design of production equipment, in addition to a number of other factors, all depend upon a number of flow parameters, such as physical properties, phase behavior and flow rates of the fluid, it is important that the flow parameters be determined accurately. As such, it may be valuable to determine the movement of fluid when present within a formation, for example, to assist in determining the value of a hydrocarbon reserve and formation, or at least a portion thereof.